Method for revascularizing a coronary vessel

ABSTRACT

A method for revascularizing a coronary vessel with a conduit through the heart wall having a diameter transition in the myocardial leg, wherein blood flow is in the direction of transition from larger to smaller diameter. A method for revascularizing a coronary vessel using an implant with a myocardial leg having a maximum cross-sectional area proximate a first end, and inserting the first end through the myocardium into a heart chamber so that the implant directs blood flow into the coronary vessel. A transmyocardial implant with a myocardial leg including point of minimum diameter and a first end with a larger diameter, and a vessel leg in fluid communication with the myocardial leg.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/043,684filed Jan. 9, 2002 now U.S. Pat. No. 6,701,932, which is a continuationof application Ser. No. 09/326,819 filed Jun. 7, 1999, now U.S. Pat. No.6,454,794, which is a divisional of application Ser. No. 08/882,397filed Jun. 25, 1997, now U.S. Pat. No. 5,994,019, which is acontinuation-in-part of application Ser. No. 08/689,773 filed Aug. 13,1996, now U.S. Pat. No. 5,755,682, all of which are incorporated hereinby reference.

II. BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method and apparatus forperforming a coronary artery bypass procedure. More particularly, thepresent invention performs a coronary artery bypass by providing adirect flow path from a heart chamber to the coronary artery. Thepresent invention is suitable for a number of approaches including anopen-chest approach (with and without cardiopulmonary bypass), aclosed-chest approach under direct viewing and/or indirect thoracoscopicviewing (with and without cardiopulmonary bypass), and an internalapproach through catheterization of the heart and a coronary arterialvasculature without direct or indirect viewing (with and withoutcardiopulmonary bypass).

2. Description of the Prior Art

A. Coronary Artery Disease

Coronary artery disease is the leading cause of premature death inindustrialized societies. The mortality statistics tell only a portionof the story. Many who survive face prolonged suffering and disability.

Arteriosclerosis is “a group of diseases characterized by thickening andloss of elasticity of arterial walls.” DORLAND'S ILLUSTRATED MEDICALDICTIONARY 137 (27th ed. 1988). Arteriosclerosis “comprises threedistinct forms: atherosclerosis, Monckeberg's arteriosclerosis, andarteriolosclerosis.” Id.

Coronary artery disease has been treated by a number of means. Early inthis century, the treatment for arteriosclerotic heart disease waslargely limited to medical measures of symptomatic control. Evolvingmethods of diagnosis, coupled with improving techniques ofpost-operative support, now allow the precise localization of theblocked site or sites and either their surgical re-opening or bypass.

B. Angioplasty

The re-opening of the stenosed or occluded site can be accomplished byseveral techniques. Angioplasty, the expansion of areas of narrowing ofa blood vessel, is most often accomplished by the intravascularintroduction of a balloon-equipped catheter. Inflation of the ballooncauses mechanical compression of the arteriosclerotic plaque against thevessel wall.

Alternative intravascular procedures to relieve vessel occlusion includeatherectomy, which results in the physical desolution of plaque by acatheter equipped with a removal tool (e.g., a cutting blade orhigh-speed rotating tip). Any of these techniques may or may not befollowed by the placement of a mechanical support (i.e., a stent) whichphysically holds open the artery.

Angioplasty, and the other above-described techniques (although lessinvasive than coronary artery bypass grafting) are fraught with acorrespondingly greater failure rate due to intimal proliferation.Contemporary reports suggest re-stenosis is realized in as many as 25 to55 percent of cases within 6 months of successful angioplasty. See BojanCercek et al., 68 AM. J. CARDIOL. 24C-33C (Nov. 4, 1991). It ispresently believed stenting can reduce the re-stenosis rate.

A variety of approaches to delay or prevent re-blockage have evolved.One is to stent the site at the time of balloon angioplasty. Another ispyroplasty, where the balloon itself is heated during inflation. Asthese alternative techniques are relatively recent innovations, it istoo early to tell just how successful they will be in the long term.However, because re-blockage necessitates the performance of anotherprocedure, there has been renewed interest in the clearly longer-lastingbypass operations.

C. Coronary Artery Bypass Grafting

i. Outline of Procedure

The traditional open-chest procedure for coronary artery bypass graftingrequires an incision of the skin anteriorly from nearly the neck to thenavel, the sawing of the sternum in half longitudinally, and thespreading of the ribcage with a mechanical device to afford prolongedexposure of the heart cavity. If the heart chamber or a vessel isopened, a heart-lung, or cardiopulmonary bypass, procedure is usuallynecessary.

Depending upon the degree and number of coronary vessel occlusions, asingle, double, triple, or even greater number of bypass procedures maybe necessary. Often each bypass is accomplished by the surgicalformation of a separate conduit from the aorta to the stenosed orobstructed coronary artery at a location distal to the diseased site.

ii. Limited Number of Available Grafts

The major obstacles to coronary artery bypass grafting include both thelimited number of vessels that are available to serve as conduits andthe skill required to effect complicated multiple vessel repair.Potential conduits include the two saphenous veins of the lowerextremities, the two internal thoracic (mammary) arteries under thesternum, and the single gastroepiploic artery in the upper abdomen.

Newer procedures using a single vessel to bypass multiple sites haveevolved. This technique has its own inherent hazards. When a singlevessel is used to perform multiple bypasses, physical stress(e.g.,torsion) on the conduit vessel can result. Such torsion is particularlydetrimental when this vessel is an artery. Unfortunately, attempts atusing artificial vessels or vessels from other species (xenografts), orother non-related humans (homografts) have been largely unsuccessful.See LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING for MYOCARDIALREVASCULARIZATION INDICATIONS, SURGICAL TECHNIQUES AND RESULTS 38-39(1990).

While experimental procedures transplanting alternative vessels continueto be performed, in general clinical practice, there are five vesselsavailable to use in this procedure over the life of a particularpatient. Once these vessels have been sacrificed or affected by disease,there is little or nothing that modern medicine can offer. It isunquestionable that new methods, not limited by the availability of suchconduit vessels, are needed.

iii. Trauma of Open Chest Surgery

In the past, the normal contractions of the heart have usually beenstopped during suturing of the bypass vasculature. This can beaccomplished by either electrical stimulation which induces ventricularfibrillation, or through the use of certain solutions, calledcardioplegia, which chemically alter the electrolyte milieu surroundingcardiac muscles and arrest heart activity.

Stoppage of the heart enhances visualization of the coronary vessels andeliminates movement of the heart while removing the need for blood flowthrough the coronary arteries during the procedure. This provides thesurgeon with a “dry field” in which to operate and create a functionalanastomosis.

After the coronary artery bypass procedure is completed, cardioplegia isreversed, and the heart electrically stimulated if necessary. As theheart resumes the systemic pumping of blood, the cardiopulmonary bypassis gradually withdrawn. The separated sternal sections are thenre-joined, and the overlying skin and saphenous donor site or sites (ifopened) are sutured closed.

The above-described procedure is highly traumatic. Immediatepost-operative complications include infection, bleeding, renal failure,pulmonary edema and cardiac failure. The patient must remain intubatedand under intensive post-operative care. Narcotic analgesia is necessaryto alleviate the pain and discomfort.

iv. Post-Operative Complications

Once the immediate post-surgical period has passed, the most troublingcomplication is bypass vessel re-occlusion. This has been a particularproblem with bypass grafting of the left anterior descending coronaryartery when the saphenous vein is employed.

Grafting with the internal thoracic (internal mammary) artery results ina long-term patency rate superior to saphenous vein grafts. This isparticularly the case when the left anterior descending coronary arteryis bypassed. Despite this finding, some cardiothoracic surgeons continueto utilize the saphenous vein because the internal thoracic artery issmaller in diameter and more fragile to manipulation. This makes thebypass more complex, time-consuming, and technically difficult.Additionally, there are physiological characteristics of an artery (suchas a tendency to constrict) which increase the risk of irreversibledamage to the heart during the immediate period of post-surgicalrecovery.

Once the patient leaves the hospital, it may take an additional five toten weeks to recover completely. There is a prolonged period duringwhich trauma to the sternum (such as that caused by an automobileaccident) can be especially dangerous. The risk becomes even greaterwhen the internal thoracic artery or arteries, which are principlesuppliers of blood to the sternum, have been ligated and employed asbypass vessels.

v. Less Invasive Procedures

Due to the invasive nature of the above technique, methods have beendevised which employ contemporary thoracoscopic devices andspecially-designed surgical tools to allow coronary artery bypassgrafting by closed-chest techniques. While less invasive, all but themost recent closed-chest techniques still require cardiopulmonarybypass, and rely on direct viewing by the surgeon during vascularanastomoses.

These methods require a very high level of surgical skill together withextensive training. In such situations, the suturing of the bypassingvessel to the coronary artery is performed through a space created inthe low anterior chest wall by excising the cartilaginous portion of theleft fourth rib. Also, as they continue to rely on the use of thepatient's vessels as bypass conduits, the procedures remain limited asto the number of bypasses which can be performed. Because of theseissues, these methods are not yet widely available.

vi. Objectives for Improved Bypass Procedures

In view of the above, it is desirable to provide other methods by whichadequate blood flow to the heart can be re-established and which do notrely on the transposition of a patient's own arteries or veins.Preferably, such methods will result in minimal tissue injury.

While the attainment of the foregoing objectives through an open chestprocedure would, by themselves, be a significant advance, it is alsodesirable if such methods would also be susceptible to surgicalprocedures which do not require opening of the chest by surgicalincision of the overlying skin and the division of the sternum. Suchmethods would not require surgical removal of cartilage associated withthe left fourth rib, would not require the surgical transection of oneor both internal thoracic arteries, would not require the surgicalincision of the skin overlying one or both lower extremities, and wouldnot require the surgical transection and removal of one or bothsaphenous veins. In both an open and closed chest approach, it is alsobe desirable if such methods could be performed without stoppage of theheart and without cardiopulmonary bypass. However, attainment of theforegoing objectives in a procedure requiring cardiopulmonary bypasswould still be a significant advance in the art.

vii. References for Prior Art Techniques

The conventional surgical procedures (such as those described above) forcoronary artery bypass grafting using saphenous vein or internalthoracic artery via an open-chest approach have been described andillustrated in detail. See generally Stuart W. Jamieson, AortocoronarySaphenous Vein Bypass Grafting, in ROB & SMITH'S OPERATIVE SURGERY:CARDIAC SURGERY, 454-470 (Stuart W. Jamieson & Norman E. Shumway eds.,4th ed. 1986); LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIALREVASCULARIZATION: INDICATIONS, SURGICAL TECHNIQUES AND RESULTS 48-80(1990). Conventional cardiopulmonary bypass techniques are outlined inMark W. Connolly & Robert A. Guyton, Cardiopulmonary Bypass Techniques,in HURST'S THE HEART 2443-450 (Robert C. Schlant & R. Wayne Alexandereds., 8th ed. 1994). Coronary artery bypass grafting utilizingopen-chest techniques but without cardiopulmonary bypass is described inEnio Buffolo et al., Coronary Artery Bypass Grafting WithoutCardiopulmonary Bypass, 61 ANN. THORAC. SURG. 63-66 (1996).

Some less conventional techniques (such as those described above) areperformed by only a limited number of appropriately skilledpractitioners. Recently developed techniques by which to perform acoronary artery bypass graft utilizing thoracoscopy andminimally-invasive surgery, but with cardiopulmonary bypass, aredescribed and illustrated in Sterman et al., U.S. Pat. No. 5,452,733(1995). An even more recent coronary artery bypass procedure employingthoracoscopy and minimally-invasive surgery, but without cardiopulmonarybypass, is described and illustrated by Tea E. Acuff et al., MinimallyInvasive Coronary Artery Bypass Grafting, 61 ANN. THORAC. SURG. 135-37(1996).

D. Bypass with Direct Flow from Left Ventricle

1. Summary of Procedures

Certain methods have been proposed to provide a direct blood flow pathfrom the left ventricle directly through the heart wall to the coronaryartery. These are described in U.S. Pat. No. 5,429,144 dated Jul. 4,1995; U.S. Pat. No. 5,287,861 dated Feb. 22, 1994; and U.S. Pat. No.5,409,019 dated Apr. 25, 1995 (all to Wilk). All of these techniquesinclude providing a stent in the heart wall to define a direct flow pathfrom the left ventricle of the heart to the coronary artery.

As taught in each of the above-referenced patents, the stent is closedduring either systole or diastole to block return flow of blood from thecoronary artery during the heart's cycle. For example, the '861 patentteaches a stent which collapses to a closed state in response to heartmuscle contraction during systole. The '019 patent (particularly FIGS.7A and 7B) teaches a rigid stent (i.e., open during systole) with aone-way valve which closes during diastole to block return flow of bloodfrom the coronary artery.

ii. Problems

The interruption of blood flow during either diastole or systole isundesirable since such interruption can result in areas of stagnant orturbulent blood flow. Such areas of stagnation can result in clotformation which can result in occlusion or thrombi breaking lose. Suchthrombi can be carried to the coronary arteries causing one or moreareas of cardiac muscle ischemia (myocardial infarction) which can befatal. Further, the teachings of the aforementioned patents direct bloodflow with a substantial velocity vector orthogonal to the axis of thecoronary artery. Such flow can damage the wall of the coronary artery.

Providing direct blood flow from the left ventricle of the coronaryartery has been criticized. For example, Munro et al., The Possibilityof Myocardial Revascularization By Creation of a Left VentriculocoronaryArtery Fistula, 58 Jour. Thoracic and Cardiovascular Surgery, 25-32(1969) shows such a flow path in FIG. 1. Noting a fall in coronaryartery flow and other adverse consequences, the authors concluded “thatoperations designed to revascularize the myocardium direct from thecavity of the left ventricle make the myocardium ischemic and areunlikely to succeed.” Id at 31.

Notwithstanding the foregoing problems and scholarly criticism, and aswill be more fully described, the present invention is directed to anapparatus and method for providing a direct blood flow path from a heartchamber to a coronary artery downstream of an obstruction. Counter tothe teachings of the prior art, the present invention providessubstantial net blood flow to the coronary artery.

E. Additional Techniques

Methods of catheterization of the coronary vasculature, techniquesutilized in the performance of angioplasty and atherectomy, and thevariety of stents in current clinical use have been summarized. Seegenerally Bruce F. Waller & Cass A. Pinkerton, The Pathology ofInterventional Coronary Artery Techniques and Devices, in 1 TOPOL'STEXTBOOK OF Interventional Cardiology 449-476 (Eric J. Topol ed., 2nded. 1994); see also David W. M. Muller & Eric J. Topol, Overview ofCoronary Athrectomy, in 1 TOPOL'S TEXTBOOK OF INTERVENTIONAL CARDIOLOGYat 678-684; see also Ulrich Sigwart An Overview of Intravascular Stents:Old & New, in 2 TOPOL'S TEXTBOOK OF INTERVENTIONAL CARDIOLOGY at803-815.

Direct laser canalization of cardiac musculature (as opposed tocanalization of coronary artery feeding the cardiac musculature) isdescribed in Peter Whittaker et al., Transmural Channels Can ProtectIschemic Tissue: Assessment of Long-term Myocardial Response toLaser-and Needle-Made Channels, 94(1) CIRCULATION 143-152 (Jan. 1,1996). Massimo et al., Myocardial Revascularization By a New Method ofCarrying Blood Directly From The Left Ventricular Cavity Into TheCoronary Circulation, 34 Jour. Thoracic Surgery 257-264 (1957) describesa T-shaped tube placed within the ventricular wall and protruding intothe cavity of the left ventricle. Also, Vineberg et al., Treatment ofAcute Myocardial Infarction By Endocardial Resection, 57 Surgery 832-835(1965) teaches forming a large opening between the left ventricularlumen and the sponge-like network of vessels lying within themyocardium.

III. SUMMARY OF THE INVENTION

The present invention relates to a method for revascularizing a coronaryvessel with a conduit through the heart wall having a diametertransition in the myocardial leg, wherein blood flow is in the directionof transition from larger to smaller diameter. The present inventionfurther relates to revascularizing a coronary vessel using an implantwith a transmyocardial leg having a maximum cross-sectional areaproximate a first end, and inserting the first end through themyocardium into a heart chamber so that the implant directs blood flowinto the coronary vessel. The present invention also relates to atransmyocardial implant with a myocardial leg including point of minimumdiameter and a first end with a larger diameter, and a vessel leg influid communication with the myocardial leg.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a right, front and top perspective view of an L-shapedconduit for use in the present invention;

FIG. 1B is a side elevation view of the apparatus of FIG. 1A shownpartially in section to reveal an optional bi-directional flow regulatorlocated in a lumen of an anchor arm of the conduit;

FIG. 1C is a side elevation view of a conduit similar to that of FIG. 1Ashowing the addition of a capacitance pressure reservoir as analternative embodiment;

FIG. 2A is a right, front and top perspective view of a T-shaped conduitaccording to the present invention;

FIG. 2B is a side elevation view of the conduit of FIG. 2A shownpartially in section to reveal an optional bi-directional flow regulatorlocated in a lumen of an anchor arm of the conduit;

FIG. 2C is a side elevation view of the conduit of FIG. 2A shownpartially in section to reveal one optional bi-directional flowregulator located in the lumen of the anchor arm of the conduit, andanother optional bi-directional flow regulator located in anintracoronary arm of the conduit;

FIG. 2D is a side elevation view of a conduit similar to that of FIG. 2Ashowing the addition of a capacitance pressure reservoir as analternative embodiment;

FIG. 3A is a partial side elevation view of a conduit similar to that ofFIGS. 1A and 2A shown partially in section to reveal a flexible anchorarm with rigid rings ensheathed in a flexible covering as an alternativeembodiment;

FIG. 3B is a partial side elevation view of a conduit similar to that ofFIG. 3A shown in section in an extended form;

FIG. 3C is a partial side elevation view of a conduit similar to that ofFIG. 3A shown in section in a compressed form;

FIG. 4 is an anterior view of a human chest which is incisedlongitudinally to reveal a dissected pericardium and mediastinalcontents;

FIG. 5 is a magnified view of an area circled 200 in FIG. 4 illustratinga longitudinally incised coronary artery;

FIG. 6 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating a channel leadingfrom a lumen of a coronary artery and into a chamber of the heartaccording to the method of the present invention;

FIG. 7 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the partialplacement of one embodiment of the conduit of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6;

FIG. 8 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the completedplacement of one embodiment of the conduit of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6;

FIG. 9 is a partial external perspective view of a sutured coronaryartery and phantom view of the conduit of the present invention;

FIG. 10 is a schematic illustration of the use of an endovascularcatheter to catheterize the patient's coronary artery;

FIG. 11A is a cutaway side elevation view of the coronary artery of thebypass procedure illustrating an intravascular catheter withdistally-located stent prior to inflation of a catheter balloonunderlying the stent;

FIG. 11B is a cutaway side elevation view of the coronary artery of thebypass procedure illustrating the intravascular catheter withdistally-located stent following inflation of the catheter balloonunderlying the stent;

FIG. 11C is a cutaway side elevation view of a coronary arteryillustrating the stent seated to the walls of the coronary artery andthe catheter partially withdrawn following deflation of the catheterballoon;

FIG. 12 is a schematic illustration with the heart in partial cutaway ofthe use of an endovascular catheter to catheterize the patient's leftventricle.

FIG. 13A is a cutaway view of the left ventricle and a partial cutawayview of the coronary artery with seated stent illustrating the formationof a channel into the wall of the left ventricle;

FIG. 13B is a cutaway view of the left ventricle and a partial cutawayview of the coronary artery with seated stent illustrating a completedchannel through the wall of the left ventricle and deep wall of thecoronary artery at the chosen bypass site;

FIG. 14A is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating theplacement of the second intraventricular catheter within the formedchannel;

FIG. 14B is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating ablockage of the formed channel by the re-inflated balloon of theintracoronary catheter;

FIG. 14C is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating aninflation of the balloon located on the distal end of theintraventricular catheter and the seating of an overlying spiral-shapeddevice against the walls of the formed channel;

FIG. 14D is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating thedevice in its locked cylindrical shape seated against the channel wallsand the partially withdrawn second intraventricular catheter;

FIG. 15A is a right anterior superior perspective view of the deviceplaced within the formed channel in its spiral shape;

FIG. 15B is a right anterior superior perspective view of the deviceplaced within the formed channel in its cylindrical form;

FIG. 16 is a cross-sectional view of an interlocking mechanism of thedevice of FIGS. 15A and 15B in its locked position;

FIG. 17A is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery, with the device shown in FIGS. 15Aand 15B seated within the formed channel, illustrating the introductionof a third intraventricular catheter into the formed channel;

FIG. 17B is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery, with the device shown in FIGS. 15Aand 15B seated within the formed channel, illustrating a tongue andgroove interlocking of the bi-directional flow regulator equipped deviceto the device seated within the formed channel;

FIG. 18A is a schematic longitudinal cross-sectional view of abi-directional flow regulator shown in a full flow position.

FIG. 18B is the view of FIG. 18A with the bi-directional flow regulatorshown in a reduced flow position;

FIG. 18C is a transverse cross-sectional view of the bi-directional flowof FIG. 18B;

FIG. 19A is a schematic cross-section longitudinal view of analternative embodiment of a bi-directional flow regulator shown in afull flow position;

FIG. 19B is the view of FIG. 19A showing the bi-directional flowregulator in a reduced flow position;

FIG. 19C is a transverse cross-sectional view of the bi-directional flowregulator of FIG. 19B.

FIG. 20 is a schematic longitudinal cross-sectional view of a channeldefining conduit with an alternative embodiment tapered anchor arm;

FIG. 21 is a schematic longitudinal cross-sectional view of the conduitof FIG. 1A in place in a coronary artery;

FIG. 22 is a schematic cross-sectional view of a test conduit for animaltesting of the invention; and

FIG. 23 is a schematic longitudinal cross-sectional view of a conduit inplace in a coronary artery illustrating a deflecting shield to protectthe coronary artery.

V. DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the various drawing figures in which identicalelements are numbered identically throughout, a description of thepreferred embodiment of the present invention and various alternativeembodiments will now be provided.

A. Detailed Summary of the Preferred Embodiment

The invention departs from the traditional bypass approach. ather thenproviding an alternative pathway for blood to flow from an aorta to acoronary artery, the inventiion provides a blood flow path leadingdirectly from a chamber of a heart to a coronary artery at a sitedownstream from the stenosis or occlusion. Unlike U.S. Pat. Nos.5,429,144; 5,287,861 and 5,409,019 and contrary to the teachings ofthese patents, the ventricular-to-coronary blood flow path remains openduring both diastole and systole. The surgical placemnt of the apparatusof the present invention establishes this alternative pathway. Also, aswill be more fully described, the invention includes means forprotecting the coronary artery from direct impingement of high velocityblood flow.

While the invention will be described in multiple embodiments and withthe description of various surgical procedures for practicing theinvention, it will be appreciated that the recitation of such multipleembodiments is done for the purpose of illustrating non-limitingexamples of multiple forms which the present invention may take.

The presently preferred embodiment is illustrated in FIG. 1A as anL-shaped conduit 10′ with an intracoronary arm 14′ to reside in thecoronary artery (and opening downstream of an occlusion). The conduit10′ has an anchor arm 12′ extending through the heart wall with anopening 12 a′ in communication with the interior of the left ventricle.

While various minimally invasive surgical procedures are described withrespect to alternative embodiments, the presently preferred embodimentplaces the conduit 10′ into a coronary artery through an open-chestapproach to be described in greater detail with reference to FIGS. 4-9.While minimally invasive procedures are desirable, an open chestprocedure is presently preferred due to the already large number ofphysicians trained and skilled in such procedures thus making thebenefits of the present invention more rapidly available to patients whocurrently lack effective treatment.

While the various embodiments (including the presently preferredembodiment of FIG. 1A) will be described in greater detail, apreliminary description of the invention and its method of use will nowbe given with reference to FIG. 21 to facilitate an understanding of adetailed description of the invention and the alternate embodiments.

FIG. 21 is a schematic cross-sectional view of a conduit 10′ of FIG. 1Aplaced within a coronary artery 30. Coronary artery 30 has a lowersurface 40 residing against an external surface of a heart wall 42surrounding the left ventricle 44.

The wall 36 of the artery 30 defines an artery lumen 48 through whichblood flows in the direction of arrow A. In the view of FIG. 21, anobstruction 34 is shown within the lumen 48. The obstruction 34 acts toreduce the volume of blood flow along the direction of arrow A.

The conduit 10′ is a rigid, L-shaped tube having an anchor arm 12′ witha longitudinal axis X—X and an opening 12 a′ at an axial end. Theconduit 10′ may be any suitable device (e.g., rigid tube, lattice stent,etc.) for defining and maintaining a fluid pathway during contraction ofthe heart.

The conduit 10′ has an intracoronary arm 14′ with a longitudinal axisY—Y and an opening 14 a′ at an axial end. Both of arms 12′, 14′ arecylindrical in shape and define a continuous blood flow pathway 11′ fromopening 12 a′ to opening 14 a′.

The axes X—X and Y—Y are perpendicular in a preferred embodiment.Alternatively, the axes X—X, Y—Y could define an angle greater than 90°to provide a less turbulent blood flow from arm 12′ to arm 14′.

The conduit 10′ is positioned for the anchor arm 12′ to pass through apreformed opening 50 in the heart wall 42 and extending from the lowersurface 40 of the coronary artery 30 into the left ventricle 44. Theopening 12 a′ is in blood flow communication with the interior of theleft ventricle 44 so that blood may flow from the left ventricle 44directly into path 11′. The arm 14′ is coaxially aligned with thecoronary artery 30 and with the opening 14 a′ facing downstream (i.e.,in a direction facing away from obstruction 34).

Blood flow from opening 12 a′ passes through the pathway 11′ and isdischarged through opening 14 a′ into the lumen 48 of the coronaryartery 30 downstream of the obstruction 34. The outer diameter of arm 14a′ is approximate to or slightly less than the diameter of the lumen 48.

The axial length of the anchor arm 12′ is preferably greater than thethickness of the heart wall 42 such that a length L protrudes beyond theinterior surface of the heart wall 42 into the left ventricle 44.Preferably, the length L of penetration into the left ventricle 44 isabout 1-3 millimeters in order to prevent tissue growth and occlusionsover the opening 12 a′.

In addition to directing blood flow downstream in the direction of arrowA, the arm 14′ holds the conduit 10′ within the coronary artery 30 toprevent the conduit 10′ from otherwise migrating through the preformedopening 50 and into the left ventricle 44. Additionally, an upper wall14 b′ of arm 14′ defines a region 15′ against which blood flow mayimpinge. Stated differently, in the absence of an arm 14′ or region 15′,blood flow would pass through the anchor arm 12′ and impinge directlyagainst the upper wall 36 of the coronary artery 30. High velocity bloodflow could damage the wall 36, as will be more fully described,resulting in risk to the patient.

The region 15′ acts as a shield to protect the coronary artery 30 fromsuch blood flow and to redirect the blood flow axially out of opening 14a′ into the coronary artery 30. This is schematically illustrated inFIG. 23. For ease of illustration, the axis X—X of the anchor arm 12′ isshown at a non-orthogonal angle with respect to the direction A of bloodflow in the coronary artery 30 (axis X—X may be either orthogonal ornon-orthogonal to direction A). The vector B of blood flow from theanchor arm 12′ has a vector component B′ parallel to blood flow A and avector component B″ perpendicular to direction A. The region 15′ ispositioned between the wall 36 and anchor arm 12′ to prevent the bloodflow B with high vector component B″ from impinging upon wall 36. Theblood flow deflected off region 15′ has a reduced vector componentperpendicular to flow direction A and reduced likelihood of damage tothe coronary artery 30. The region 15′ may be a portion of anintracoronary arm 14′ or the arm 14′ may be eliminated with the region15′ being an axially spaced extension from arm 12′ or a separate shieldsurgically positioned within the coronary artery.

A portion 17′ of the anchor arm 12′ extends from the lower surface 40 ofthe coronary artery 30 and through the lumen 48 to the upper surface 36to block the cross-section of the coronary artery upstream from opening14 a′. The region 17′ acts as a barrier to impede or prevent anydislodged portions of the obstruction 34 from passing the conduit 10′and flowing downstream through the coronary artery 30.

The present invention maintains blood flow through the conduit 10′during both diastole and systole. Therefore, while the net blood flow isin the direction of arrow A, during diastole, blood will flow in adirection opposite of that of arrow A.

The constantly open pathway 11′ results in a net flow in the directionof arrow A which is extraordinarily high and sufficient to reduce oravoid patient symptoms otherwise associated with an obstruction 34.Specifically, certain aspects of the apparatus and method of the presentinvention have been preliminary tested in animal studies. FIG. 22schematically illustrates the tests as the placement of a test conduit10* in the coronary artery 30′ of a pig. For purposes of the tests, astainless steel T-shaped conduit 10* is used having aligned openings 14a*, 16 a* positioned within the coronary artery 30′ and with a thirdopening 12 a* protruding 90° out of the coronary artery 30′. The conduit10* has a uniform interior diameter of 3 millimeters to correspond insizing with a 3 millimeter lumen of coronary artery 30′. The thirdopening 12 a* is connected by a 3 millimeter conduit 13 to a 3millimeter rigid Teflon (PTFE) sleeve 13 a which was passed through theheart wall 42′ into the left ventricle 44′. The conduit 13 and sleeve 13a do not pass through the coronary artery 30′.

In the view of FIG. 22, the direction of net blood flow is shown byarrow A. A first closure device in the form of a suture loop 300surrounds the artery 30′ adjacent the upstream opening 14 a* of theconduit 10*. The loop 300 provides a means for closing the upstreamopening 14 a* by selectively constricting or opening the loop 300 toselectively open or block blood flow through the coronary artery 30′.The first loop 300 permits the test to simulate blockage of the coronaryartery 30′ upstream of the conduit 10*.

A flow meter 304 to measure volumetric flow of blood downstream of theconduit 10* is placed adjacent downstream opening 16 a*. A secondclosure device 302 functioning the same as loop 300 is placed on conduit13 to selectively open or close blood flow through conduit 13.

When the second device 302 is closed and the first device 300 is open,the conduit 10* simulates normal blood flow through a healthy coronaryartery 30′ and the normal blood flow can be measured by the flowmeasuring device 304. By opening second device 302 and closing the firstdevice 300, the test conduit 10* can simulate the placement of a conduitsuch as that in FIG. 21 with an obstruction located on the upstream sideof the conduit. The flow meter 304 can then measure flow of bloodthrough the conduit 10* during both diastole and systole.

The results of the tests indicate there is a substantial net forwardblood flow (i.e., volumetric forward flow less volumetric retro-flow)with the second device 302 remaining open during both diastole andsystole and with the first device 300 closed to simulate an obstruction.Specifically, in the tests, net blood flows in excess of 80 percent ofnormal net forward blood flow were measured.

The amount of back flow through a conduit can be controlled without theneed for providing a valve within the conduit. Conveniently referred toas flow “bias”, a volumetric forward flow greater than a volumetricrearward flow can be manipulated through a variety of means includingsizing of the interior diameter of the conduit, geometry of the conduit(e.g., taper, cross-sectional geometry and angle) and, as will be morefully discussed, structure to restrict rear flow relevant to forwardflow.

The sizing of the interior diameter of the flow pathway 11′ can beselected to minimize back flow. As will be more further discussed, thenet flow increases with a reduction in the diameter as suggested bysimulation modeling of flow through a conduit. One method in which shearrate and flow bias can be controlled is by providing a tapered diameterfor a narrower diameter at opening 14 a′ than at opening 12 a′. Theselection of the conduit geometry (e.g., an angled anchor arm as shownin FIG. 23 or a tapered geometry as will be discussed with reference toFIG. 20) can be selected to modify the degree to which the conduit isbiased to net forward flow (i.e., the conduit offers less resistance toforward flow than to retro-flow) without stopping or blockingretro-flow.

The substantial net blood flow measured in animal testing through theinvention is extraordinarily high when compared to minimum acceptablelevels of net blood flow following traditional bypass techniques (i.e.,about 25 percent of normal net blood flow). Further, the results arecounter-intuitive and contradictory to the prior teachings of the art ofU.S. Pat. Nos. 5,429,144; 5,287,861 and 5,409,919 and theafore-mentioned Munro et al. article. In addition, the present inventionprovides a conduit with a shielding area to prevent damaging impingementof blood flow directly onto the coronary artery wall as well asproviding a blocking area to prevent the migration of debris from anobstruction to a location downstream of the conduit.

Having provided a summarized version of the present invention withreference to the schematic drawings of FIGS. 21 and 22, a more detaileddescription of the present invention as well as a detailed descriptionof alternative embodiments and alternative surgical procedures will nowbe provided.

B. Embodiments with an Open Chest Approach

1. The Apparatus of the Present Invention for Use in the Open ChestApproach

As will be more fully described, the present invention places anapparatus for defining a blood flow conduit directly from a chamber of aheart to a coronary artery downstream of an occluded site. Beforedescribing the surgical methods for placing such an apparatus, anapparatus of the present invention will be described. The apparatus ofthe present invention can be a variety of shapes or sizes, and is notmeant to be limited as to size, shape, construction, material, or in anyother way by the following examples in which a preferred embodiment isillustrated.

a. T-Shaped Device

With initial reference to FIGS. 2A, 2B, 2C, 2D and 2E, relatedembodiments of an apparatus according to the present invention are shownas a rigid T-shaped conduit 10 (a preferred L-shaped conduit 10′ havingalready been summarized and to be later described in detail). Theconduit 10 is hollow and includes two axially-aligned intracoronary arms14, 16 terminating at open ends 14 a, 16 a. An anchor arm 12 (having anopen end 12 a) extends perpendicularly to arms 14, 16. The entireconduit 10 is hollow to define a blood flow conduit 11 providing bloodflow communication between open ends 12 a, 14 a and 16 a.

As will be more fully discussed, arms 14 and 16 are adapted to be placedand retained within a lumen of a coronary artery on a downstream side ofan occlusion with open ends 14 a, 16 a in blood flow communication withthe lumen. The anchor arm 12 is adapted to extend through and beretained in a heart wall (e.g., a wall of the left ventricle) with theopen end 12 a in blood flow communication with blood within the chamber.When so placed, the conduit 10 defines a surgically-placed conduitestablishing direct blood flow from the heart chamber to the artery. By“direct” it is meant that the blood flow does not pass through the aortaas occurs in traditional bypass procedures. The conduit 10 issufficiently rigid such that it defines an open blood flow path duringboth diastole and systole.

b. Optional Forward Flow Bias

While unobstructed back flow is preferred, partially restricted backflow can be provided. As will be more fully described, back flow can becontrolled by the geometry of the conduit. The following describes apresently less preferred alternative embodiment for controlling backflow.

FIG. 2B illustrates use of an optional bi-directional flow regulator 22within the conduit 10 and positioned in anchor arm 12. Thebi-directional flow regulator 22 permits unimpeded flow in the directionof arrow A (i.e., from open end 12 a to open ends 14 a, 16 a) whilepermitting a reduced (but not blocked) reverse flow.

FIG. 2C illustrates the use of a first bi-directional flow regulator 22as well as a second bi-directional flow regulator 26 in arm 16 near theopen end 16 a of the apparatus. The second bi-directional flow regulator26 permits unimpeded blood flow in the direction of arrow B. The secondbi-directional flow regulator 26 is used to permit a reduced (but notzero) back flow of blood in an upstream direction within the coronaryartery. For example, the coronary artery may not be completelyobstructed and may have a reduced flow past an obstruction. The use ofthe T-conduit 10 with axially aligned arms 14, 16 takes advantage ofsuch reduced flow and supplements such flow with blood through anchorarm 12. As will be described, the conduit 10 is placed with the arms 14,16 in the lumen of the artery with opening 16 a positioned on theupstream side (i.e., nearest to, but still downstream of, theobstruction).

As indicated above, the flow regulator 22 is a bi-directional flowregulator. By this it is meant that the flow regulator 22 does not blockflow of blood in any direction. Instead, the flow regulator 22 permits afirst or maximum flow rate in one direction and a second or reduced flowrate in a second direction. The flow regulator is schematicallyillustrated in FIGS. 18A through 19C. In each of these embodiments, thearrow A indicates the direction of blood flow from the left ventricle tothe coronary artery.

FIGS. 18A through 18C illustrate one embodiment of a bi-directional flowregulator 22. FIGS. 19A through 19C illustrate an alternative embodimentof a bi-directional flow regulator 22. The regulator 22 of FIGS. 18Athrough 18C shows a butterfly valve 222 mounted in the anchor arm 12 ofa rigid conduit 10. Valve 222 may be pivoted (in response to blood flowin the direction of arrow A) between a position with the plate 222generally parallel to the walls 12 of the conduit 10 as illustrated inFIG. 18A. The plate 222 can be rotated (in response to blood flowreverse to arrow A) to a position angled relative to the walls 12 of theconduit 10 as illustrated in FIG. 18B. FIG. 18A may be convenientlyreferred to as a full flow position. FIG. 18B may be convenientlyreferred to as a reduced flow position. FIG. 18C is a cross-section ofthe conduit 10 when the plate 222 is in the reduced flow position.

The plate 222 is sized relative to the conduit 10 such that thecross-sectional area of the conduit 10 which remains open is sufficientto permit about 20% of the blood flow (measured volumetrically) to flowback through the conduit 10 in a direction opposite to that of arrow Aduring diastole. As a result, during systole, blood flow from the heartto the coronary artery urges the plate 222 to the full flow position ofFIG. 18A such blood may flow unobstructed through the device to thecoronary artery. During systole, the blood (due to pressuredifferentials between the coronary artery and the left ventricle) willflow in a direction opposite of that of arrow A causing the plate 222 torotate to the position of FIG. 18B and 18C. However, even in the reducedflow position, the plate 222 is prevented from moving to a full closedposition such that flow through the device is never blocked and insteadmay proceed with a back flow of about 20% (volumetrically measured) ofthe normal flow in the direction of A.

FIGS. 19A through 19C show an alternative design of the conduit 10 withthe flow regulator 22 a in the form of three leafs 222 a, 222 b, 222 cwhich, in response to blood flow from the left ventricle to the coronaryartery, open to a full open position shown in FIG. 19B and move to arestricted flow position in FIGS. 19A and 19C in response to back flow.The leaves 222 a, 222 b, 222 c are provided with openings 223 to permitflow through the leaves 222 a, 222 b, 222 c at all times.

It is believed that providing a back flow of about 20% (20% being anon-limiting example of a presently anticipated desired back flow rate)of the volumetric anterograde flow is necessary. This is essentialbecause it allows the channel of the conduit 10 and the mechanicalelements of the flow regulator 22 to be washed by the retrograde flow.This ensures that no areas of stagnant flow occur. Areas of stagnation,if allowed, could result in clot formation which could result in thrombioccluding the conduit or breaking loose. Thrombi could be carrieddownstream into the coronary arteries to cause one or more areas ofcardiac muscle ischemia (i.e., a myocardial infarction) which could befatal. Back flow necessary to wash the components can be achievedthrough either a conduit 10 which has a constant opening through bothsystole and diastole (i.e., conduit 10 of FIG. 2A without the use of abi-directional flow regulator 22) or with a device coupled with abidirectional flow regulator 22 (FIGS. 2B-2C) which permits a 20% flowrate back flow during diastole.

c. L-Shaped Device

Preferably, an L-shaped conduit 10′ (FIGS. 1A, 1B, 1C) is used tocompletely bypass the coronary obstruction. An L-shaped conduit 10′ hasan anchor arm 12′ with an open end 12 a′. Unlike conduit 10, conduit 10′has only one intracoronary arm 14′ perpendicular to arm 12′. Arm 14′ hasan open end 14 a′ and conduit 10′ is hollow to define a continuous fluidpathway 11′ from end 12 a′ to end 14 a′. In application, arm 14′ isplaced within the lumen of an artery. End 14 a′ faces downstream from anobstruction. Arm 12′ is placed through the heart wall with end 12 a′ influid communication with blood within the heart chamber. As illustratedin FIG. 1B, the anchor arm 12′ can include a bi-directional flowregulator 22′ similar to bi-directional flow regulator 22 of conduit 10.

d. Optional Flexible Anchor Arm

Conduit 10, 10′ may be rigid, or have varying flexibilities. Regardlessof such flexibility, the conduit 10, 10′ should be sufficiently rigidfor pathway 11, 11′ to remain open during both diastole and systole.FIGS. 3A, 3B and 3C demonstrate one embodiment where the anchor arm(i.e., elements 12, 12′ of FIGS. 1A and 2A) is comprised of a number ofrings 17 surrounded by a membrane 18. In FIGS. 3A-3C, only anchor arm 12is shown. It will be appreciated that anchor arm 12′ may be identicallyconstructed.

In the embodiment of FIGS. 3A-3C, the rings 17 can be constructed ofTeflon, and the surrounding membrane 18 can be constructed of adouble-walled Dacron sheath into which the rigid supporting rings 17 aresewn. In this embodiment, the rings 17 provide structural strength. Thestructural strength maintains an open lumen or conduit 11 leading intothe coronary artery by preventing the conduit 11 from collapsing byreason of contraction of the heart muscle surrounding the anchor arm 12.The series of rings 17 provide a degree of flexibility which allows achannel formed through the heart chamber muscular wall (receiving anchorarm 12) to be angled or curved. In addition, the flexibility of thesurrounding sheath 18 in concert with the rigid rings 17 will allow theanchor arm 12 to expand, FIG. 3B, and contract, FIG. 3C, with thecontractions and relaxations of the surrounding cardiac musculature.

It should be noted that, because of the semi-rigid nature of the anchorarm 12 constructed in this manner, a method of attaching that end of theanchor arm in contact with the inner surface of a chamber of a heart canbe useful. In the example illustrated, this attaching mechanism 19 is arigid flange 12 a. It will be appreciated that other mechanisms ofattachment, such as suturing, biologically gluing, etc. are alternativeoptions.

e. Optional Blood Reservoir

The apparatus of the present invention (as thus described) provides apath 11 through which blood flows from a chamber of a heart and into acoronary artery. Additionally, such a device can store blood underpressure for a period of time prior to its introduction into a coronaryartery. As depicted in the embodiments of FIGS. 1C and 2D, this aspectof the conduit 10, 10′ of the present invention is referred to as acapacitance pressure reservoir (CPR) 24, 24′.

Blood flow through the normal coronary artery is cyclical. Blood flow isincreased during diastole (when the heart muscle is in a relaxingstate), and decreases or reverses during systole (when the heart muscleis in a contracting state). See, e.g., F. Kajiya et al., VelocityProfiles and Phasic Flow Patterns in the Non-Stenotic Human LeftAnterior Descending Coronary Artery during Cardiac Surgery, 27CARDIOVASCULAR RES. 845-50 (1993).

The pressure gradient across the lumens 12 a, 12 a′, 14 a′the presentinvention will vary over the cardiac cycle. For example, during systole,the contraction of the heart muscles will generate high relativepressures within the left ventricle.

The pressures within the coronary arterioles and capillaries distal tothe bypass site can also be high during this time, due to the externalcompression of the contracting cardiac musculature surrounding thesevessels. This is particularly true for the vessels of themicrocirculation deep within the heart which serve the endocardium.

The optional CPR 24, 24′ stores the pressurized blood during systole fordelivery to the heart muscles via the coronary circulation duringdiastole when pressures are reduced. In essence, the CPR 24, 24′ servesa function similar to the elastic connective tissue of the thick-walledaorta. The necessary function of the CPR 24, 24′ is to store blood underhigher pressure, and to later provide that stored blood to themicrocirculation when the external pressures on that microcirculationare reduced.

As depicted in FIGS. 1C and 2D the bi-directional flow regulators 22,22′ provide full blood flow in the direction of A, which is from achamber of a heart into the conduit 10, 10′ via the lumen 11, 11′. Thepressure on the blood within the chamber of a heart will be greatestwhen the surrounding cardiac musculature is in the contracting phase ofthe cardiac cycle. Because it is during this phase of the cardiac cyclethat the external pressure on the coronary artery microcirculation isalso highest, blood flow through the lumen 11, 11′ of the conduit 10,10′ could be limited. To counteract this tendency, the conduit 10, 10′is equipped with a reservoir 24, 24′ which stores this pressurized bloodflowing from a chamber of the heart during the cardiac contraction.

The reservoir, or CPR 24, 24′ is schematically illustrated in FIGS. 1C,2D. It can be appreciated that the conduit 10, 10′ is provided with afluid passage 28, 28′ in communication with pathway 11, 11′. The passage28, 28′ communicates with an expandable volume (or storage chamber) 27,27′ defined by a movable wall 31, 31′ contained within a fixed housing33, 33′. Springs 29, 29′ between wall 31, 31′ and housing 33, 33′ urgethe wall 31, 31′ to move to reduce the size of volume 27, 27′. Thesprings 29, 29′ are pre-loaded to exert a force on wall 31, 31′ lessthan a force exerted by blood within volume 27, 27′ during thecontraction phase of the cardiac cycle, but greater than the forceexerted by blood within volume 27, 27′ during the relaxation phase ofthe cardiac cycle.

The conduit 10, 10′ is constructed in a manner which allows blood toflow into the storage chamber 27, 27′ of the conduit 10, 10′ through thelumen 11, 11′ of arm 28, 28′ of the conduit when the cardiac musculatureis contracting. When blood is flowing into the storage chamber 27, 27′,the kinetic energy of the flowing blood is converted to potentialenergy, and stored in 29, 29′. During the relaxation phase of thecardiac musculature, the potential energy stored in 29, 29′ of the CPR24, 24′ is then re-converted to kinetic energy in the form of blood flowout of the storage chamber 27, 27′ of the conduit 10, 10′ via the lumen11, 11′ of arm 28, 28′ of the conduit.

While the CPR 24, 24′ is illustrated with a movable wall 31, 31′ andsprings 29, 29′ to define a variable volume, other designs can be used.For example, the CPR 24, 24′ can be a balloon-like structure. As itfills with blood, the pressure on that blood increases through thestretching of an elastic component of a balloon. In another embodiment,the CPR, 24, 24′, can be a hollow bag, made of a material which iselastic, but impermeable to liquids, and pliable similar to a plasticbag. When the heart contracts, blood is forced through lumen 11, 11′ ofarm 28, 28′ of the apparatus 10, 10′ of the invention into thecollection bag.

The incorporation of bi-directional flow regulators 22, 22′ within theanchoring arm 12, 12′ of the conduit 10, 10′ provide most (about 80%) ofthe flow of blood out of the device during diastole to the coronaryartery via the lumen 11′ 11′ of arms 14 a, 14 a′, 16 a of the device, ofthe conduit 10, 10′. Similarly, the incorporation of the bi-directionalflow regulator 26 within the intracoronary arm 16 of the T-shapedconduit 10, when employed with the bi-directional flow regulator 22within the anchor arm 20 of the conduit 10, would provide most of theflow of blood out of the device during diastole to the portion of thecoronary artery distal to the bypass site via the downstream lumen 11 ofarm 14 a.

f. Sizing of the Conduit

The inner and outer cross-sectional diameters of a coronary arterydecreases with the distance from the arterial origin. Eventually, theartery branches into a number of arterioles, which feed the capillarybed of the coronary arterial microcirculation.

The typical diameter of a lumen of a coronary artery is, in general,species specific; increasing with heart size. In humans, this lumendiameter is dependent upon which artery is being evaluated, but usuallyranges from 1.0 to 4 mm in diameter, and decreases with distance fromthe aortic origin. In the preferred embodiment, the cross-sectionalouter diameter of the intracoronary arms 14, 14′, 16 of the device ofthe present invention should effectively approximate the diameter of thelumen of the coronary artery being bypassed, at the bypass site. Thisallows the complete re-approximation of the previously openedsuperficial wall of the coronary artery during surgical closure, withouthigh suture or staple tension resulting. In the most preferredembodiment, the outer diameter of the intracoronary arms 14, 14′, 16 ofthe conduit 10, 10′ of the present invention is equal to the diameter ofthe lumen of the coronary artery which is being bypassed, at the bypasslocation. When a CPR is placed, the artery wall may need to be expandedby the addition of a patch, such as Dacron, well known in the art.

Also, due to smooth muscle relaxation and secondary vascular dilation,the cross-sectional diameter of a lumen of a coronary artery willincrease with the oxygen demand of cardiac muscle during times ofstress. The cross-sectional inner diameter of the intracoronary arms 14,14′, 16 of the conduit 10, 10′ of the present invention shouldeffectively approximate that diameter necessary to provide adequateblood flow through the downstream lumen of the conduit to effectivelyoxygenate the cardiac musculature normally supplied by themicrocirculation of the coronary artery. In the preferred embodiment,the cross-sectional inner diameter of the intracoronary arms 14, 14′, 16of the conduit 10, 10′ of the present invention should effectivelyapproximate that diameter necessary to provide adequate blood flowthrough the lumen of the device to effectively oxygenate the cardiacmusculature normally supplied by the microcirculation of the coronaryartery during both times of cardiovascular resting and stress.

If necessary, an initial approximation of the required cross-sectionalouter diameter of the intracoronary arms 14, 14′, 16 of the conduit 10,10′ of the present invention can be gained by standard radiographictechniques. Also, in the alternative embodiment apparatus when abi-directional flow regulator 22, 22′ is desired, the operating pressureof the bi-directional flow regulator 22, 22′ (i.e., the pressure atwhich the flow regulator moves from a reduced back-flow to a fullforward flow position) can be determined by the dynamic measurements ofcoronary artery pressure, blood flow, and heart chamber pressuresthrough selective catheterization with standard techniques. See MinoruHongo et al., 127(3) AM. HEART J. 545-51 (March 1994).

During the coronary artery bypass procedure, the most appropriate sizingof the intracoronary arms 14, 14′, 16 of the conduit 10, 10′ of thepresent invention can be re-assessed. This can be accomplished byprobing the distal and ,if needed, the proximal aspects of the coronaryartery at the chosen bypass site with blunt instruments of known outerdiameters. Such sizing by probes is well-known in the literature. Tofacilitate the effective matching of the external diameter of theintracoronary arms 14, 14′, 16 of the conduit 10, 10′ of the presentinvention to the lumen 34 of the coronary artery to be bypassed, anassortment of conduits of the present invention of various diameters canbe available for the surgeon to select from.

The anchor arm 12, 12′ is sized to maximize net blood flow from the leftventricle to the coronary artery. Through simulation testing, acounter-intuitive indication is that maximizing the diameter of anchorarm 12, 12′ is not desirable. For example, such simulation assumingdiameters of 3.00 mm, 2.25 mm and 1.50 mm for an unrestricted fistula(i.e., without a flow regulator 22) suggests that the smaller diameterof 1.50 mm most closely approximates normal coronary blood flow andminimizes back flow thus maximizing net forward flow.

It is desirable that the anchor arm 12, 12′ protrudes into the heartchamber such that end 12 a is spaced from the heart wall. This preventstissue growth over end 12 a.

Finally, it will be noted that the anchor arm 12 defines a longitudinalaxis (e.g., axis X—X in FIG. 18A). The region 15 of arms 14, 14intersects axis X—X. The region 15 acts as a deflection surface toprevent high velocity blood flow from arm 12 impinging directly upon thecoronary artery wall. Instead, the high velocity blood flow impingesupon region 15 and is directed axially into the coronary artery. As aresult, the coronary artery wall covered by region 15 is protected fromdamage which would otherwise be caused by the high velocity blood flowand the blood components are transitioned to axial flow with a minimumof cell damaging shear.

FIG. 20 shows a still further embodiment 10″ where the anchor arm 12″has a longitudinal axis X′—X′ at a non-orthogonal angle relative to theaxis Y′—Y′ of the coronary arms 14″, 16″. Further, the anchor arm 12″has a taper. In other words, the arm 12″ is widest at opening 12 a ″.The taper and angle act to reduce blood flow velocity and to restrictback flow (arrows B) while facilitating forward flow (arrow A′). Also,the blood in the forward flow A′ impacts against the deflection region15″ at an angle to reduce impact of blood cells.

2. The Method of the Present Invention Using the Open Chest Approach

a. General

The method of the present invention is suitable for performing a varietyof surgical cardiac procedures. The procedures may be performedutilizing an open-chest approach, or through minimally invasiveapproaches by the creation of access means into the chest, or throughpercutaneous access utilizing intracoronary and intraventricularcatheterization. Dependent on the invasiveness of the approach utilized,the heart can be allowed to pulse normally, be slowed by varyingamounts, or stopped completely. A significant period of complete heartstoppage can necessitate the use of supportive cardiopulmonary bypass.

The method of the present invention for performing a coronary arterybypass procedure will now be described in detail. The patient who is toundergo the procedure can be prepared in a conventional manner forcardiac bypass surgery. The patient preparation, anesthesia utilized,and access route to the coronary circulation, will vary depending uponthe invasiveness of the specific procedure chosen.

b. Preparation for the Procedure

i. General Preparations

Standard techniques of general preparation for open-chest surgery inwhich cardiopulmonary bypass is utilized have been widely reported. See,e.g. LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIALREVASCULIZATION (1990). In one embodiment of the methods of theinvention where an open-chest procedure and cardiopulmonary bypass isutilized, the patient can be prepared for surgery as outlined by VonSegesser.

General preparations for open-chest surgery in which cardiopulmonarybypass is not utilized have been published by Buffolo et al., 61 ANN.THORAC. SURG. 63-66(1996). In one embodiment of the methods of theinvention where an open-chest procedure without cardiopulmonary bypassis utilized, the patient can be prepared for surgery as outlined byBuffolo.

General preparations for closed-chest surgery, to be performed usingthoracoscopy and where cardiopulmonary bypass is utilized, have beenoutlined by Sterman et al., U.S. Pat. No. 5,452,733 (1995). In oneembodiment of the methods of the invention where a closed-chestprocedure and cardiopulmonary bypass is utilized, the patient can beprepared for surgery as outlined by Sterman.

General preparations for closed-chest surgery to be performed usingthoracoscopy, but where cardiopulmonary bypass is not utilized, havebeen published by Acuff et al., 61 ANN. THORAC. SURG. 135-37 (1996). Inone embodiment of the methods of the invention where a closed-chestprocedure without cardiopulmonary bypass is utilized, the patient can beprepared for surgery as outlined by Acuff.

General preparations for percutaneous coronary artery bypass graftingutilizing intracoronary and intraventricular catheterization and withoutcardiopulmonary bypass have been described by Wilk in hisafore-mentioned U.S. patents. Preparations can include the sterilescrubbing and draping of at least one groin to permit access to afemoral artery for catheterization of the coronary vasculature and thesterile scrubbing and draping of the right superior anterior chest wallto permit access to the innominate artery for catheterization of theleft ventricle. Further suggested preparations can include thoseoutlined by Sterman and Acuff for thoracoscopic surgery with and withoutcardiopulmonary bypass, respectively.

ii. Anesthesia Prior to and During the Procedure

Most often, the patient will be placed under general anesthesia prior tothe procedure. In one embodiment, standard cardiac operative anesthetictechniques, such as premedication with diazepam, induction with propofoland sufentanil, and maintenance with desflurane can be employed. Onoccasion, less than general anesthesia can be utilized. Less thangeneral anesthesia is well known in the literature. When theinvasiveness of the procedure is minimal, such as when the procedure isto be carried out via intracoronary and intraventricularcatheterization, or when the risks of general anesthesia to theindividual patient outweighs the risks of less than general anesthesiawith regard to the particular procedure planned, less than generalanesthesia can be induced. Selective ventilation of the lungs can beachieved through the placement of a double-lumen endobronchial tubewhich independently provides for the intubation of the left and rightmain stem bronchi. An intraesophageal probe can be placed to facilitatecardiac monitoring and the synchronization of power to the laser, whendeemed useful.

iii. Access to the Heart and Coronary Vasculature for the Procedure

Following preparation, access to the patient's coronary arterialvasculature can be attained through a variety of techniques, dependentupon the route of access chosen.

Von Segesser has reported a method of access to the coronary arterialvasculature when utilizing an open-chest approach and cardiopulmonarybypass. In one embodiment, utilizing an open-chest approach withcardiopulmonary bypass, access to the coronary vasculature can beobtained as reported by Von Segesser.

Buffolo et al. has reported an open-chest approach to the coronaryarterial vasculature when performed without cardiopulmonary bypass. SeeBuffolo et al., 61 ANN. THORAC. SURG. 63-66 (1996). In one embodimentutilizing an open-chest approach without cardiopulmonary bypass, accessto the coronary vasculature can be obtained as reported by Buffolo.

Sterman et al. has reported a method of access to the coronary arterialvasculature when a closed-chest approach with cardiopulmonary bypass isutilized. See Sterman et al., U.S. Pat. No. 5,452,733 (1995). Stermanpositions a plurality of access trocar sheaths along the patient's leftand right anterolateral chest wall. These trocar sheaths provide accessto the coronary vasculature, and allow the temporary repositioning ofthe heart to facilitate the performance of the procedure. Therepositioning is accomplished utilizing grasping tools introducedthrough the appropriate trocar sheaths. Visualization during thisprocedure can be either indirectly via thoracoscopy, or directly via a‘window’ placed in the left middle anterior chest wall by the surgicalremoval of the fourth rib. Access to the bypass site can therefore beobtained by following the techniques outlined by Sterman. Theinstruments to be used in the procedure can also be similar to thosedescribed by Sterman.

Acuff et al. has described a method of access to the coronary arterialvasculature when a closed-chest approach without cardiopulmonary bypassis utilized. See Acuff et al., 61 ANN. THORAC. SURG. 135-37 (1996).Similar to the techniques of Sterman, Acuff positions a plurality ofaccess trocar sheaths along the patient's left and right anterolateralchest wall. Also similar to Sterman, Acuff surgically establishes anaccess space, or window in the left anterior chest wall through theremoval of the left fourth rib cartilage. The trocar sheaths, in concertwith this window, allow the temporary repositioning of the heart, andaccess to the coronary arterial vasculature. Visualization during thisprocedure can be either indirectly via thoracoscopy, or directly via thewindow. Access to the bypass site can therefore be obtained by followingthe techniques outlined by Acuff. The instruments to be used in theprocedure can also be similar to those described by Acuff.

Access to a chamber of a heart and a coronary artery when the bypass isperformed through the percutaneous approach of intracoronary andintraventricular catheterization can be obtained as follows. Access to acoronary artery can be obtained by the introduction of a catheter intothe left or right femoral artery through an arterial cut down procedure.The catheter can then be fed retrograde past the descending aorta,through the ascending aorta, and into the coronary artery by standardcatheterization techniques. In a preferred embodiment, access to achamber of the left side of a heart can be obtained by the introductionof a catheter into the innominate artery, also through an arterial cutdown procedure. In the most preferred embodiment, access to the leftventricle is obtained by the introduction of a catheter into theinnominate artery and the advancement of this catheter into the leftventricle. In this embodiment, the catheter is advanced through theascending aorta, past the aortic valve. and into the left ventricle.Techniques by which the left ventricle is catheterized are well known inthe literature.

3. Open Chest Approach

In the coronary artery bypass graft procedures of the present invention,a chamber of a heart provides blood to a coronary artery. The method ofthe present invention can accomplish this by establishing one or morechannels through the wall of a chamber of a heart which lead directlyfrom a chamber of a heart into a coronary artery at a site distal to thenarrowing or blockage. The methods of the invention in variousembodiments can achieve the establishment of such a channel or channelsthrough a variety of techniques.

Referring now to FIGS. 4, 5, 6, 7, 8, and 9, an exemplary open-chestprocedure, which may or may not include cardiopulmonary bypass, by whicha coronary artery bypass procedure may be accomplished will bedescribed. The open-chest approach affords maximal access to, andvisualization of, the coronary vasculature; although at the expense ofinjury to normal tissue.

Through the methods of the present invention, the conduit 10, 10′ of thepresent invention, which provides blood from a chamber of a heart 43directly into a coronary artery 30, is placed. To illustrate theinvention, only placement of conduit 10′ is discussed. It will beappreciated that conduit 10 can be similarly placed. In addition,examples will be limited to the embodiment of the conduit of theinvention as illustrated in FIG. 1A.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

First, the chest cavity is entered, and pericardium 52 incisedanteriorly, to expose a coronary artery 30 (having an obstruction 34) tobe bypassed. This is illustrated in FIG. 4.

Second, cardiopulmonary bypass may be initiated by a variety of standardtechniques as outlined by George Silvay et al., Cardiopulmonary Bypassfor Adult patients: A Survey of Equipment and Techniques, 9(4) J.CARDIOTHORAC. VASC. ANESTH. 420-24 (August 1995).

Third, if bypassed, the heart is slowed and/or stopped by a variety ofstandard techniques. One standard technique is to electrically induceventricular fibrillation. Another standard technique is warm or coldblood cardioplegia, delivered antegrade or retrograde, and intermittentor continuous, as outlined by Gerald D. Buckberg, Update on CurrentTechniques of Myocardial Protection, 60 ANN. THORAC. SURG. 805-14(1995).

Fourth, the heart is inspected and coronary arteries identified. Thenarrowed or occluded coronary artery 30 can be visually identified, andan appropriate site distal or downstream from the occlusion 34 chosen.

Fifth, blood flow through the target coronary artery 30 is halted bystandard techniques. For example, standard techniques include clampingthe aorta above the coronary ostia with an arterial clamp.Alternatively, in the beating heart procedure, the flow of blood withinthe coronary artery 30 can be halted by forming a loop around the artery30 with suture either proximally, or both proximally and distally, andapplying appropriate tension on the suture or sutures, or tying thesuture or sutures.

Sixth, depending on the degree of exposure deemed necessary, theepicardium overlying the coronary artery at the selected bypass site isincised. This exposure can facilitate locating the lumen of the coronaryartery 30 via palpation.

Seventh, as shown in FIG. 5, the superficial wall 36 of the coronaryartery 30 is longitudinally incised by standard techniques, such asincision with a scalpel, electrosurgical cutting device, or similartool; taking care not to damage the deep wall of the artery. Thisinitial incision can be lengthened, if necessary, to accommodate theintracoronary arms 14′ using standard tools such as fine angledscissors.

Eighth, a channel 50 is initiated into the deep coronary arterial wall40 and through the musculature 42 of a chamber of a heart. In thepreferred embodiment, the chamber of a heart is the left ventricularchamber of the heart. The channel 50 can be initiated by standardtechniques such as awl punching, incising, use of a laser, or the like.The channel 50 is then extended into the chamber of a heart, in thiscase the left ventricle 44, by standard techniques (such as punchingwith a trocar 46, incising with a scalpel blade, electrosurgical cuttingwith an electrosurgical cutting tool, laser or radio frequency ablation,blunt dissection, etc.).

Ninth, once a channel extending through the entire thickness of a wall42 of a chamber of a heart is formed, it can be systematically sized bythe passage of standard probes.

Tenth, through palpation, inspection, and probing of the distal andproximal coronary artery lumen 48, a conduit 10′ of appropriatedimensions is selected, as outlined above.

Eleventh, as illustrated in FIGS. 7 and 8, the anchor arm 12′ isinserted into the formed channel 50. The intracoronary arm 14′ is thenseated within the lumen 48 of the coronary artery 30.

Twelfth, as shown in FIG. 9, the longitudinal incision 38 previouslyincised in the anterior wall 36 of the coronary artery 30 is surgicallyre-approximated. The re-approximation can be performed by a number ofconventional techniques, including suturing 52, laser welding,microstapling, and the like.

Thirteenth, the clamps or sutures closing off blood flow to the coronaryartery are released.

Fourteenth, contractions of the heart, if previously stopped, arereinitiated by standard electrostimulation or the reversal ofcardioplegia and the patient is slowly weaned from cardiopulmonarybypass by standard techniques.

Fifteenth, the pericardium, sternum, and overlying skin of the chest isre-approximated and surgically closed by standard, conventionaltechniques.

Sixteenth, anesthesia is reversed and the patient revived by standardtechniques.

D. Embodiments for a Closed Chest Approach

1. The Apparatus of the Present Invention for Use in the Closed ChestApproach

A closed chest approach according to the method of the present inventionmay use the conduit 10, 10′ as described above. Such a procedure willnow be described. Following this description, a closed chest approachusing alternative embodiments of the apparatus of the invention will bedescribed.

2. The Method of the Present Invention Using the Closed Chest Approach

An exemplary closed-chest procedure, without cardiopulmonary bypass, bywhich a coronary artery bypass may be accomplished will now bedescribed. The closed-chest approach is less invasive than theopen-chest approach, although providing the surgeon with somewhat poorervisualization and limited direct access to both the chambers of theheart and coronary artery bypass site.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

First, a plurality of access trocar sheaths is positioned anterior andlaterally along the left and right chest walls as outlined by Acuff etal.

Second, a space in the left low anterior chest wall may be formed byremoval of the fourth rib cartilage, as outlined by Acuff et al. In thisembodiment, the heart and coronary artery can be both directly viewedvia this space or window, as well as indirectly visualized via athoracoscope.

Third, a standard pericardiotomy is performed using a scalpel orelectrosurgical cutting tool introduced through the left lateral chesttrocar sheaths while viewing under thoroacoscopy. The pericardium can beexcised and either spread open, or removed from the thoracic cavity asoutlined by Acuff et al.

Fourth, if necessary, the heart can be rotated within the mediastinum.Direct access and visualization through the formed chest wall space canrequire rotation of the heart. Rotation of the heart can be accomplishedby the grasping of the heart by tools inserted through access trocarsheaths located along the left and right chest wall as described bySterman et al. Alternatively, traction on sutures placed in thepericardium can distract the heart allowing appropriate directvisualization of the area to be bypassed as described by Acuff et al. Inanother alternative procedure, the heart can be accessed from thepatient's back with an endoscope for implantation of the stent in theposterior vascular beds which are not currently accessible by minimallyinvasive techniques.

Fifth, once the coronary artery to be bypassed is identified andwell-visualized; snare sutures of 5-0 polypropylene are placed at leastproximally to the target area as described by Acuff et al.

Sixth, the heart rate can be pharmacologically slowed to approximately40 beats/minute to minimize motion within the operative field asdescribed by Acuff et. al. Nitroglycerin and heparin can also beadministered to reduce cardiac ischemia and prevent clottingrespectively as outlined by Acuff et al.

Because cardiopulmonary bypass is omitted in this embodiment,intermittent coronary artery occlusion to induce ischemicpreconditioning, as well as transesophageal echocardiography to reviewcardiac wall motion changes, can be utilized as described by Acuff etal. The epicardium can be incised over the area selected for bypass andthe anterior surface of the artery cleared under direct visualizationthrough the space or window, or via remote instruments inserted throughthe trocar sheaths under thoracoscopic guidance.

Seventh, in situations where the coronary artery can be directly viewed,the lumen 48 of the coronary artery is identified by palpation. Eitherunder direct visualization, or under thoracoscopic guidance and usinginstruments manipulated through the trocar sheaths, the superficial wall36 of the coronary artery is then longitudinally opened. As above, careis taken to leave the deep wall 40 of the artery undamaged. The incision38 can be enlarged, as necessary, to accommodate the intracoronary arms14, 14′, 16 of the conduit 10, 10′ using fine angled scissors. Thisenlargement can be performed with standard surgical scissors underdirect viewing through the window, or via other surgical instrumentsremotely manipulated following their insertion through the trocarsheaths.

Eighth, a channel 50 through the heart wall is initiated by incising orlaser ablating into the deep wall 40 of the coronary artery. This alsocan be performed by standard surgical tools under direct viewing, or bythe remote manipulation of specialized instruments introduced throughthe trocar sheaths and viewed thoracoscopically. The channel 50 is thenextended through the deep coronary arterial wall 40, through underlyingcardiac musculature 42, and into the underlying chamber of the heart 44by incising with a scalpel or electrosurgical cutting blade, laserablation, blunt dissection, or the like. In the preferred embodiment, achamber of a heart 44 is one of the two chambers of the left side of theheart. In the most preferred embodiment, a chamber of a heart 44 is theleft ventricle.

Ninth, the channel 50 extending through the entire thickness of amuscular wall 42 can be systematically sized by the passage of standardmeasuring probes. These standard measuring probes, with fixed and knowntip diameters, can be similarly used to size and determine the proximaland distal patency of the coronary artery being bypassed.

Tenth, through direct and/or thoracoscopic inspection of the coronaryartery lumen 48, or by probing as outlined above, an appropriatelydimensioned conduit 10, 10′ of the present invention is selected. As inthe case of the open-chest approach (outlined above), an array ofconduits 10, 10′ of various sizes can be available for the operation.

Eleventh, either under direct control and visualization, or by indirectmanipulation and thoracoscopic viewing, the anchoring arm 12, 12′ of theconduit 10, 10′ of the invention is inserted into the formed channel 50.By similar techniques the remaining intracoronary arm or arms 14, 14′,16 of the conduit 10, 10′ are seated within the lumen 48 of the coronaryartery 30 being bypassed. In one embodiment where the procedure isperformed under thoracoscopic viewing, the conduit 10, 10′ can beintroduced into the cardiac cavity through the space or windowpreviously formed within the anterior inferior aspect of the left chestwall. In this embodiment, the conduit 10, 10′ can be grasped, onceintroduced into the chest cavity, by surgical instruments insertedthrough the trocar sheaths and remotely manipulated into position. Inthis manner the anchor arm 12, 12′ of the conduit 10, 10′ is theninserted into the channel formed 50 via the remote manipulation of theseinstruments.

Twelfth, the incision present in the superficial wall 38 of the coronaryartery 30 is closed by conventional surgical techniques such assuturing, laser welding, microstapling, and the like. When closure is byindirect thoracoscopic versus direct viewing, suturing, laser welding,microstapling and the like can be accomplished by utilizing surgicalinstruments remotely manipulated following their introduction throughthe trocar sheaths.

Thirteenth, upon completion of placement of the conduit 10, 10′ of thepresent invention, the heart, if rotated, can be returned to its normalorientation.

Fourteenth, all heart manipulating devices are removed from the chestcavity.

Fifteenth, contractions of the heart can be allowed to return to theirnormal resting rate by the discontinuation of intravenous esmolol anddiltiazem, if utilized.

Sixteenth, the pericardium 52 is partially or completelyre-approximated. An external drain can be placed inside the pericardium,as needed, as described by Acuff et al.

Seventeenth, the trocar sheaths are removed, and all thoracic puncturessurgically repaired in a conventional manner.

Eighteenth, anesthesia is reversed and the patient revived by standardtechniques.

E. Embodiments with the Catheter-Controlled Approach Referring now toFIGS. 10, 11, 12, 13, 14, 15, and 16, an exemplary coronary arterybypass procedure performed through catheterization will be described.This approach allows no direct visualization of the coronaryvasculature, although the chamber of the heart could be indirectlyvisualized during the procedure by equipping the intraventricularcatheter with a standard fiber-optic device, if desired. Because theprocedure is performed through catheters introduced remotely, normaltissue injury is minimized.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

In the embodiment to be described, cardiopulmonary bypass isunnecessary. However, the procedure would be in no way limited ifcardiopulmonary bypass were performed.

First, an intracoronary catheter 120 (FIG. 10) is inserted via anincision in the groin 126 and advanced within the femoral artery 124.Through continued advancement within the descending aorta 128, and theascending aorta 122, the coronary artery 30 is entered.

Dependent on the degree of narrowing or occlusion of the coronaryartery, standard angioplasty, atherectomy, or some similar procedure canbe optionally performed if passage of the catheter tip 136 (FIG. 11A) ishindered. Angioplasty, arthrectomy, and the like could optionallyprecede the catheter-controlled bypass procedure.

If desired, the heart may be slowed while catheterizing the coronaryvasculature, during the construction of a channel or channels 50 leadingfrom a chamber of a heart 44 into a lumen of a coronary artery 30itself, or both. Such slowing can improve visualization of the cathetersas facilitated by fluoroscopy or the alternative radiologic techniquesby which the procedure can be performed. Standard pharmacologic methods,as described above, to slow the heart are well known in the literature.

Second, the intracoronary catheter 120 is advanced within the coronaryarterial vasculature tree to the target location through standardcatheter manipulation techniques. The proper location of theintracoronary catheter tip 136 in relation to the targeted bypass sitecan be determined through standard radiographic techniques.

Third, as shown in FIGS. 11A-11C, a balloon 130 located on the distalend of the intracoronary catheter 120 is inflated (FIG. 11B). Inflationof the balloon 130 causes a stent 134 located circumferentiallysurrounding the balloon 130 to be seated against the coronary arterialwalls 36, 40. The stent 134 is a hollow expandable stent having acut-out area 135 along the cylindrical wall of the stent 134, forreasons that will become apparent. The stent 134 is positioned atplacement within the coronary artery in a manner that the cut-out 135 isjuxtaposed against the deep wall 40 of the coronary artery 30 uponinflation of the intracoronary catheter balloon 130.

Fourth, the balloon 130 is deflated (FIG. 11C) and the catheter 120withdrawn into the ascending aorta 122 leaving the expanded stent 134 inplace.

Fifth, an intraventricular catheter 140 is inserted into the innominateartery 144 via an incision in the anterior superior right chest wall 142as shown in FIG. 12. The intraventricular catheter 140 is advanced in aretrograde fashion through the ascending aorta 22, and into the chamberof the left side of the heart. By continued advancement, theintraventricular catheter 140 is extended past the semilunar valves 148and into the left ventricle 44. Throughout the procedure, the locationof, the intraventricular catheter 140 within a chamber of a heart 44 canbe ascertained by either indirect visualization employing standardfiber-optic instrumentation inherent to the intraventricular catheter,or and/or by standard radiographic techniques.

Sixth, a channel 50 can be ablated (FIGS. 13A-13B) through both a wallof a chamber of a heart 42 and the deep wall of a coronary artery 40utilizing and ablating tip 132. Such ablating devices are weel known inthe literature and can include a laser, a radio frequency device, or thelike. Power to the ablating tip 132 can be synchronized via theintraesophageal probe such that ablation occurs at a recurring aspect ofthe cardiac cycle. Such synchronization of devices to physiologicalfunction is well known in the literature. The ablation can be indirectlyobserved via fiber optic associated with the intraventricular catheter140. Alternatively, the location of the ablating tip 132 can determinedby standard radiographic techniques.

Seventh, once a channel 50 through the heart chamber wall 42 is formed,the intracoronary catheter 120 is re-advanced into the coronary artery30.

Eighth, the balloon 130 on the distal end of the intracoronary catheter120 is re-inflated upon reaching the target bypass site, as illustratedin FIGS. 14A and 14B. Inflation of the intracoronary catheter balloon130 seals the formed channel 50 so that blood is prevented from flowingfrom the coronary artery lumen 48, through the formed channel 50, andinto a chamber of the heart 44. Note, though, that the inflation of theintracoronary catheter balloon 130 still allows blood to perfuse thedownstream portion of the coronary artery 30. This is because theintracoronary catheter 120 is equipped with channels 138 which allowblood to pass internally within the intracoronary catheter 120 from theupstream portion of the coronary artery 30, and to exit the catheterinto the downstream portion of the coronary artery 30.

Ninth, the ablating catheter 140 is removed from the body completely.

Tenth, a second intraventricular catheter 160 is inserted into theinnominate artery 144 at the arterial cut-down site 142, as shown inFIG. 12. The intraventricular catheter 160 is next advance in aretrograde fashion into the ascending aorta 22. By continuedadvancement, the intraventricular catheter 160 is finally extended pastthe semilunar valves 148 and into the left ventricle 44.

This intraventricular catheter is equipped with a inflatable balloon 60on the catheter's distal end, and a stent-forming device 61circumferentially surrounding the balloon 60 on the catheter's distalend (FIGS. 14A-14D).

The stent forming device 61 is a spiral sheet shown separately in FIGS.15A and 15B. Initially, the device 61 is a sheet formed in a spiralshape as shown in FIG. 15A to present a reduced diameter smaller thanthe diameter of the formed channel 50. In response to expanding forces(e.g., expansion of a balloon 60 within device 61), device 61 expands toa cylinder as shown in FIG. 15B. Interlocking tabs 61 a and recesses 61b on opposing edges of the device 61 define a locking mechanism 62 toretain the device 61 in a cylindrical shape. The cylindrical shape ofdevice 61 after expansion of the balloon 60, as shown in FIG. 15B, islarger in diameter than the spiral shape of device 61 prior to expansionof the balloon 60, as shown in FIG. 15A. The device 61 as expanded issized to be retained within the formed channel 50 upon expansion.

Throughout this portion of the procedure, the location of this secondintraventricular catheter 160 within a chamber of a heart 44 can beascertained by either indirect visualization employing standardfiber-optic instrumentation inherent to the second intraventricularcatheter, or and/or by standard radiographic techniques.

Eleventh, the tip 180 (FIG. 14A) of the second intraventricular catheter160 is introduced into and advanced within the formed channel 50.

Twelfth, with the tip 180 of the second intraventricular catheter 160near or abutting the side of the intracoronary catheter balloon 130, aballoon 60 surrounding circumferentially the tip of the secondintraventricular catheter 160, is inflated. As shown in FIGS. 14C and14D, inflation of the balloon 60 causes the device 61 locatedcircumferentially around the balloon 60 located on the end of the secondintraventricular catheter 160 to become seated against the walls of theformed channel 50.

As shown in FIG. 16, the device 61, is locked into the cylindricalposition when the underlying balloon 60 is inflated by an interlockingmechanism 62 constructed as part of the device 61.

Thirteenth, the balloon 60 on the intraventricular catheter tip isdeflated, and the catheter removed from the body, as shown in FIG. 14D.

Fourteenth, a third intraventricular catheter 70 is inserted at theinnominate artery access site 142. This third intraventricular catheter70 is then advanced in a retrograde fashion into a chamber of the leftside of a heart, as outlined above.

This third intraventricular catheter 70 is equipped with a hollow tube71 on its distal tip which can interlock to the device 61 previouslyplaced within the formed channel 50, as shown in FIGS. 17A and 17B.

Fifteenth, the hollow tube 71 is forwarded within the formed channel 50,and interlocked to the device 61. In one embodiment, the hollow tube 71can partially insert into the device 61 previously seated within theformed channel 50.

The hollow tube 71 can, but may not necessarily, be equipped with abidirectional flow regulator 74 to provide full blood flow in thedirection of arrow C with reduced (but not blocked) blood flow oppositethe direction of arrow C. An array of such hollow tubes 71 of variousdimensions can be available to the surgeon at the operative procedure.

Sixteenth, the balloon 130 on the end of the intracoronary catheter 120is deflated.

Seventeenth, angiographic dye can be introduced into a chamber of theheart through a port internal to the third intraventricular catheter 71.The introduction of angiographic dye can allow the blood flow to bevisualized under fluoroscopy, digital subtraction angiography, orsimilar standard techniques. By such radiographic examination, bloodflow directly from a chamber of a heart into a coronary artery can beascertained. In cases where a bi-directional flow regulator 74 isutilized, the bi-directional flow from a chamber of a heart and into acoronary artery and the flow rates can be verified.

Eighteenth, the third intraventricular catheter 70 is withdrawn from thebody through the innominate incision site 142.

Nineteenth, the intracoronary catheter 120 is withdrawn from the bodythrough the femoral incision site 126.

Twentieth, the sites of the innominate incision 142 and femoral incision126 are surgically re-approximated through standard closure techniques.

Twenty-first, anesthesia is reversed and the patient revived by standardtechniques.

Changes and Modifications

Although the foregoing invention has been described in detail by way ofillustration and example, for purposes of clarity of understanding, itwill be obvious that changes and modifications may be practiced withinthe scope of the appended claims.

1. A method for performing a coronary vessel bypass procedure forsupplementing a flow of blood to a coronary vessel at a heart wall, themethod comprising: forming an opening through the heart wall such thatan axis of the opening intersects the coronary vessel; positioning aconduit through the opening with a first end of the conduit protrudinginto a heart chamber beyond an interior surface of the heart wall and asecond end in fluid communication with the vessel; and directing bloodflow through the conduit from the heart chamber to the coronary vessel.2. The method according to claim 1, wherein the conduit extendscompletely through the heart wall and projects beyond an exteriorsurface of the heart wall.
 3. The method according to claim 1, whereinthe conduit is open during at least systole.
 4. The method according toclaim 1, wherein the conduit is selected with the first end dimensionedfor insertion into and retention within the heart wall, and the secondend having an outer diameter sized to approximate a diameter of a lumenof the coronary vessel.
 5. The method according to claim 1, comprisingdirecting blood flow through the conduit to reduce direct impingement ofthe blood flow upon a wall of the coronary vessel by providing adeflecting surface positioned in the path of such direct impingement. 6.The method according to claim 1, wherein the conduit is rigid along itsentire length.
 7. The method according to claim 1, wherein the conduitprotrudes by 1 to 3 mm into the heart chamber.
 8. The method accordingto claim 1, further comprising selecting the conduit such that it has aninterior diameter so as to minimize backflow.
 9. The method according toclaim 1, wherein the interior diameter of the conduit ranges from 1 to 4mm.
 10. The method according to claim 1, wherein the vessel is acoronary artery.
 11. A method for supplementing a flow of blood to acoronary vessel, the method comprising: placing a conduit in a heartwall between a heart chamber and the coronary vessel so that a bloodflow path directly between the heart chamber and a posterior of thecoronary vessel remains open during both systole and diastole, whereinplacing the conduit includes percutaneously inserting the conduit. 12.The method of claim 11, wherein a first end of the conduit protrudesinto the chamber beyond an interior surface of the heart wall.
 13. Themethod of claim 11, wherein the blood flow path is formed at a site inthe coronary vessel positioned between an obstruction in the coronaryvessel and tissue of the heart to be supplied with blood by the coronaryvessel.
 14. The method of claim 11, wherein the conduit ispercutaneously inserted in a collapsed configuration.
 15. The method ofclaim 14, wherein the conduit is expanded in the heart wall.
 16. Themethod of claim 11, wherein placing the conduit includes expanding theconduit in the heart wall.
 17. The method of claim 11, wherein theconduit includes a portion placed into the coronary vessel.
 18. Themethod of claim 17, wherein placing the portion of the conduit into thecoronary vessel includes expanding the portion of the conduit.
 19. Themethod of claim 18, wherein the portion of the conduit is expanded via aballoon.
 20. The method of claim 11, wherein the conduit extendscompletely through the heart wall.
 21. The method of claim 11, whereinthe conduit is valveless.
 22. A method for supplementing a flow of bloodto a coronary vessel, the method comprising: placing a conduit in aheart wall between a heart chamber and the coronary vessel so that ablood flow path directly between the heart chamber and a posterior ofthe coronary vessel remains open during both systole and diastole,wherein a first end of the conduit protrudes into the chamber beyond aninterior surface of the heart wall.
 23. The method of claim 22, whereinthe blood flow path is formed at a site in the coronary vesselpositioned between an obstruction in the coronary vessel and tissue ofthe heart to be supplied with blood by the coronary vessel.
 24. Themethod of claim 22, wherein placing the conduit includes percutaneouslyinserting the conduit.
 25. The method of claim 24, wherein the conduitis percutaneously inserted in a collapsed configuration.
 26. The methodof claim 25, wherein the conduit is expanded in the heart wall.
 27. Themethod of claim 22, wherein placing the conduit includes expanding theconduit in the heart wall.
 28. The method of claim 22, wherein theconduit includes a portion placed into the coronary vessel.
 29. Themethod of claim 28, wherein placing the portion of the conduit into thecoronary vessel includes expanding the portion of the conduit.
 30. Themethod of claim 29, wherein the portion of the conduit is expanded via aballoon.
 31. The method of claim 22, wherein the conduit extendscompletely through the heart wall.
 32. The method of claim 22, whereinthe conduit is valveless.
 33. A method for supplementing a flow of bloodto a coronary vessel, the method comprising: placing a conduit in aheart wall between a heart chamber and the coronary vessel so that ablood flow path directly between the heart chamber and a posterior ofthe coronary vessel remains open during both systole and diastole,wherein placing the conduit includes expanding the conduit in the heartwall.
 34. The method of claim 33, wherein a first end of the conduitprotrudes into the chamber beyond an interior surface of the heart wall.35. The method of claim 33, wherein the blood flow path is formed at asite in the coronary vessel positioned between an obstruction in thecoronary vessel and tissue of the heart to be supplied with blood by thecoronary vessel.
 36. The method of claim 33, wherein placing the conduitincludes percutaneously inserting the conduit.
 37. The method of claim36, wherein the conduit is percutaneously inserted in a collapsedconfiguration.
 38. The method of claim 37, wherein the conduit isexpanded in the heart wall.
 39. The method of claim 33, wherein theconduit includes a portion placed into the coronary vessel.
 40. Themethod of claim 39, wherein placing the portion of the conduit into thecoronary vessel includes expanding the portion of the conduit.
 41. Themethod of claim 40, wherein the portion of the conduit is expanded via aballoon.
 42. The method of claim 33, wherein the conduit extendscompletely through the heart wall.
 43. The method of claim 33, whereinthe conduit is valveless.
 44. A method for supplementing a flow of bloodto a coronary vessel, the method comprising: placing a conduit in aheart wall between a heart chamber and the coronary vessel so that ablood flow path directly between the heart chamber and a posterior ofthe coronary vessel remains open during both systole and diastole,wherein the conduit includes a portion placed into the coronary vessel,wherein placing the portion of the conduit into the coronary vesselincludes expanding the portion of the conduit.
 45. The method of claim44, wherein a first end of the conduit protrudes into the chamber beyondan interior surface of the heart wall.
 46. The method of claim 44,wherein the blood flow path is formed at a site in the coronary vesselpositioned between an obstruction in the coronary vessel and tissue ofthe heart to be supplied with blood by the coronary vessel.
 47. Themethod of claim 44, wherein placing the conduit includes percutaneouslyinserting the conduit.
 48. The method of claim 47, wherein the conduitis percutaneously inserted in a collapsed configuration.
 49. The methodof claim 48, wherein the conduit is expanded in the heart wall.
 50. Themethod of claim 44, wherein placing the conduit includes expanding theconduit in the heart wall.
 51. The method of claim 44, wherein theportion of the conduit is expanded via a balloon.
 52. The method ofclaim 44, wherein the conduit extends completely through the heart wall.53. The method of claim 44, wherein the conduit is valveless.